CSI Fraud: researchers craft fake DNA evidence

Researchers have demonstrated it's possible to remove all the DNA from samples …

If there's one application of modern genetics that the public has not only accepted but embraced, it's the use of DNA testing in criminal investigations. Courts have accepted DNA evidence as definitive, and it's difficult to imagine a movie or TV show that focuses on law enforcement but declines to use DNA testing as a plot device. The reason is simple: given a valid DNA sample, the tests can match it to its source with probabilities that exclude the rest of our planet's population. Those probabilities still hold, but some researchers have now looked into whether it's possible to fake a valid DNA sample, and they have come up with a disturbing answer: just about any molecular biology lab has the tools to do so.

DNA evidence is appealing largely because it's rigorously scientific: we have empirical data about the prevalence of different genetic variations in the population, and it's easy to calculate the probability of any individual carrying a specific combination of those variants. Look at enough of them, and you can lower that probability to the point where it's less than one in several billion, meaning that DNA's owner is likely to be the only person on earth with that precise combination.

In contrast, as recent reports have indicated, there's not a lot of science to the rest of forensic science. As the authors of the new paper point out, in contrast to the science behind DNA, "other types of forensic evidence, such as ballistics, blood-spatter analysis, and ?ber analysis... rely on expert judgment and have limited connection to established science. [DNA] is even considered to be more reliable than eyewitness evidence, which is known to suffer from a relatively high rate of errors."

Which is what makes their report disturbing. The forensic processing pipeline includes a variety of methods to identify likely sources of DNA, ranging from identifying obvious points of contact like the grip of a gun, to locating sources of biological material, such as blood and saliva spatters. DNA is then isolated from these sources. But there's no way to determine if the DNA that actually wound up in or on the sample is actually the same DNA it started with.

As the researchers demonstrate, it's possible to exploit this loophole with a vengeance. Purified DNA can be smeared all over the surface of your choice, such as a gun grip. It's also possible to eliminate the original DNA from blood and saliva samples using a standard piece of lab equipment called a centrifuge, which spins rapidly in order to separate components of liquids based on their density. So, for example, it's possible to spin all the cells that contain DNA out of a saliva sample, or separate the white blood cells out of a blood sample. The liquid that's left behind looks like a valid biological sample, but contains none of the original DNA.

All that's left then is to replace the original DNA. Since most of the forensic tests are performed using a standard set of DNA fragments amplified by PCR, the authors simply took an environmental sample ("blood, dry saliva stains on absorbent paper, skin scrapings, hair, and smoked cigarette butts were collected"), amplified up the same fragments, and then spiked the purified blood and saliva with this DNA. They estimate that a library of about 425 DNA fragments would be enough to fake a match to just about anyone in existing DNA databases—without any DNA from that individual ever being obtained.

Of course, if any forensic technician goes digging beyond the standard genetic markers, problems would become apparent pretty quickly. Still, the authors are ready for this eventuality. A technique has been around since 2001 that allows the entire human genome to be amplified, starting from a sample with fewer than 10 cells. Here, you'd definitely need a DNA sample from the individual you're trying to frame, but it wouldn't take much of one.

To show that their results were more than an intellectual curiosity, the authors shipped some fabricated samples off to a third-party DNA testing facility. As far as the facility was concerned, everything looked legitimate.

Fortunately, in identifying the problem, the researchers have come up with a solution. DNA inside human cells picks up a chemical modification called methylation; DNA amplified in a test tube doesn't. It's possible to determine whether or not a given stretch of DNA has been methylated using standard lab techniques, although these are a bit laborious and time-consuming, and it's the sort of technique that hasn't made its way into forensic training yet. Still, testing for methylation in a DNA sample should provide an important quality control on the sample—at least until biologists figure out how to apply methylation in a controlled manner.

It would be tempting to view this as an arms race between the sophistication of fabrication and forensic techniques, but the fact is that your garden variety criminal is unlikely to have the skills and equipment needed to pull a fake off. What it may do is undermine the general confidence in the use of DNA evidence. There's simply no way of knowing a priori which cases might have a molecular biologist with a vested interest, and therefore which samples need to be tested for tampering. It appears that we'll need to start testing methylation patterns in every case in order to retain confidence in the general techniques.

In the meantime, the most immediate effect of the paper is that it's almost certainly set off a spasm of scriptwriting among those responsible for TV whodunnits.

Originally posted by Evil Peer:Most other types of evidence can be faked also. While DNA testing may take a hit, its probably still more reliable than the other types of evidence listed.

Problem is that prosecutors are having a hard time already with jurors thinking shows like CSI and other court/police dramas are actually accurate (it's rare that CSI evidence wraps things up so nice and neat as shown on TV - people really are dim). Reality is that you're not always going to have DNA evidence, and now it can really be a matter of contention knowing DNA could be faked.

Personally, I'm not so sure I'd want a jury of my "peers" to be deciding my fate. Then again, I've seen some real wacky judges out there as well.

...and this is why base colelcted evidence should be run through more than 1 independent lab in addition to FBI/police labs. It need not even be required on all cases, simply something the defense can request (and pay for at their own expense) in order to provide contrary eveidence. Any cases where the state provides DNA evidence, but can;t provide enough source sample for 3rd party validation should be excluded.

not to mention, regardless of the DNA, they actually have to prove you were actually there (no viable alibi), and that you had some resemblence of a motive, or reasonably doubt will still be easy to obtain.

DNA is not proof of guilt, it's merely a part of a larger collection of facts in the evidence bucket. If it can be faked, it's even less stron evidence.

I suspect that most evidence can be forged. I believe that fingerprints were first forged in the 1890's (using dichromated gelatin as the resist medium). The problem is more the unreasonable and unquestioning stance taken by many prosecutors and jurors as to the value of evidence.

Somebody with access to discarded condoms in an area of casual prostitution can easily frame an innocent for rape or sexual abuse - and it would probably be exceptionally difficult to defend against in the current environment unless the defendant had true proof of being somewhere else at the time - and even that might not help with some prosecutors.

"In contrast, as recent reports have indicated, there's not a lot of science to the rest of forensic science."

I don't think thats an accurate statement. The report its refering to is the National Academy of Sciences report. In that report is laid out 13 recommendations for bettering forensic science. Those 13 recommendations are a result of the forensic community themselfs through the Consortium of Forensic Science Organizations asking the National Academy of Science to include forensic science in its report. Without their asking then the forensic science aspect would have never been included. The report in no way says there is not science involved in forensics, it only supplies 13 recommendations for improving the science already there, and some of the recommendations don't even deal with science but instead with standardization and budgeting such as interoperability of automated fingerprint identification systems. So this 'recent report' did not indicate anything of the sort as the article claims.

The person that spearheaded the effort to have the forensics recommendations included in the report is Kenneth F. Martin who is the Commanding Officer of the Crime Scene Services Section of the Massachusetts State Police and Chairman of the Board for the Internation Association for Identification (IAI). His email is public if you want to contact him at: kenneth.martin@theiai.org

You guys realize they're talking about removing the genetic material...like the nucleus, et.al...from the evidence and replacing it with someone elses. Sure, evidence can be faked, but someone would need to really, REALLY know what the hell they're doing here, and have access to some sophisticated tools to do so. I don't think this is the kind of thing small-time criminals or framers/blackmailers would be pulling off.

It's hardly news that a deliberately fraudulent effort to frame somebody by police and lab techs can succeed. There is ongoing work to make sure the handling of evidence is honest and careful, just as there is ongoing work to prevent crime itself. This started millenia ago and will continue long after we are all dead and gone. Hopefully the good guys win most of the time, and the world will never be perfect.

Are small time criminals a big concern in cases involving evidence tampering or mishandling at crime labs?

I think what more at issue here is the fact that much of what crime labs do the public, thanks large in part to fictional programs, is eager to accept as irrefutable evidence when in truth it's pure junk science that's been used to convict countless innocent people of serious crimes, no laughing matter.

In a recent Popular Mechanics article it was stated that: "Forensic science...was not developed by scientists. It was created by cops—often guided by little more than common sense—looking for reliable ways to match patterns from clues with evidence tied to suspects. What research has been done understandably focuses on finding new techniques for putting criminals in jail."

Commenting on the article judicial watch bulldog Radley Balko wrote: "In other words, where science is about process, forensics tends to be more concerned with outcomes."

The matter becomes even more serious with the "wise" Latina's addition to the US Supreme Court. Until a few weeks ago a defendant had no right to cross examine a forensics expert, the very person sure to give most damning evidence in many cases. Sotomayor many believe presented the opportunity will bring about reversal, once again making cross examination off limits.

Of course all this should mean little to you, it's always very comfortable as long as someone else is doing the suffering and dying, well, until you're the wrongly accused that is, at which point I suspect things may suddenly develop a more serious tone very rapidly.

The matter becomes even more serious with the "wise" Latina's addition to the US Supreme Court. Until a few weeks ago a defendant had no right to cross examine a forensics expert, the very person sure to give most damning evidence in many cases. Sotomayor many believe presented the opportunity will bring about reversal, once again making cross examination off limits.

What on Earth are you talking about? Every defendant has the right to cross examine anyone testifying against them. Just as every prosecutor has the right to cross examine anyone testifying for the defense (defendant included if they choose to testify).

Originally posted by Tundro Walker:Sure, evidence can be faked, but someone would need to really, REALLY know what the hell they're doing here, and have access to some sophisticated tools to do so. I don't think this is the kind of thing small-time criminals or framers/blackmailers would be pulling off.

You don't understand, DA's are often highly motivated to get convictions even if it means framing innocent people. Many a politician gets voted in on a "get tough on crime" platform, and this often means not just more arrests, but more convictions. It is not criminals looking to be let off who would perpetrate fake DNA, it is the labs themselves, under pressure from politicians, law enforcement, and perhaps corruption through payoffs, who might use this to get innocent suspects convicted, not to get guilty suspects free! (although that would be a "side effect") Some might dismiss the scenario as paranoid, except that DNA evidence has already shown how other types of evidence has been mis-used to frame innocent people. To rephrase a recent movie tagline: "Who's watching the lab workers?"

Cuvtixo, I agree with you. I was looking at it from a strictly functional/mechanical aspect, which the article seemed to be focusing on (removing DNA markers from a cell and replacing it with another person's).

However, the "human aspect" overrides all of that. Even if DNA testing were 100% fool-proof, humans are not, thus mix-ups, willful alterations, and even just malicious prosecution can factor in. You're correct that an entity which isn't watched can tend to get egotistical, sloppy, etc.